The present invention relates to a data recording medium. The data recording medium has a radiation-sensitive recording layer. A laser beam is focused on the radiation-sensitive recording layer to form a pit therein, thereby recording optical data. The optical data recorded in this manner can be read out.
A conventional data recording medium is known wherein a recording layer 2 of a metal such as Te, Bi, Mn or the like is formed on a substrate 1 of glass or a synthetic resin by vacuum deposition, sputtering or the like (FIG. 1). Another conventional data recording medium is known wherein an anticorrosive protective layer 3 is formed on the surface of the recording layer 2 (FIG. 2). The protective layer 3 is generally made of an organic or inorganic material which has resistance to corrosion. The protective layer of an inorganic material is formed on the recording layer into a thin film of less than 5,000 A in thickness, for example, by vacuum deposition, sputtering or the like of silicon dioxide, silicon monoxide, indium oxide or the like. On the other hand, the protective layer of an organic material is formed on the recording layer into a thin film of about 1 to 100.mu., for example, by dissolving in a solvent a polyvinyl chloride resin, styrene resin or the like to provide a solution of the resin and by applying the solution by a suitable means such as a spinner, a roll coater, an applicator or the like.
However, when the protective layer of an inorganic material is formed on the recording layer by vacuum deposition or sputtering, cracks tend to form in the recording layer and/or protective layer after a certain period of time. On the contrary, when the protective layer of an organic material is formed in place of the protective layer of an inorganic material, the recording layer may flow during application or during curing steps of the protective layer of the organic material. For this reason, the formation of the protective layer of the organic material is cumbersome, and cracks tend to form after a certain period of time.